gtkContainerAdd instead of this function.gtkScrolledWindowAddWithViewport(object, child)objectchildGdkWindow, and takes
the size of the child to be the size of its toplevel GdkWindow.
This will be very wrong for most widgets that support native scrolling;
for example, if you add a widget such as GtkTreeView with a viewport,
the whole widget will scroll, including the column headings. Thus,
widgets with native scrolling support should not be used with the
GtkViewport proxy.
A widget supports scrolling natively if the
set_scroll_adjustments_signal field in GtkWidgetClass is non-zero,
i.e. has been filled in with a valid signal identifier.